Comparison Between Direct and Competitive Models to Investigate Variation of Carcass and Ham Quality Traits in Heavy Pigs

Social interactions among animals raised in pens can aff ect their performance. In this study direct and competitive models were compared to investigate the infl uence of social genetic eff ects on variation of carcass weight (CW), carcass lean meat content (LM) and ham round shape (RS) in heavy pigs. Four sequential models including, in addition to sex and slaughter group fi xed eff ects, the random eff ects of the social group, litter (full-sibs family), direct and social genetic eff ects of pigs were evaluated. Social group and litter eff ects accounted for about 4 and 3% of the phenotypic variance, respectively. When social genetic eff ects were added to model, a small social heritability was estimated for all traits (from 0.3 to 0.7% of the phenotypic variance). A negative correlation between direct and social eff ects was estimated for LM and RS, reducing the total heritable variance available for selection. Model comparison showed that the best fi t was provided by the model including only direct additive genetic eff ects of pigs. So, this model seems still preferable for the genetic evaluation of the investigated traits.